Deducing the Big Apple
by TheOtherHalfBloodPrince
Summary: Sherlock is hot on the trail of a serial killer, and his pursuit leads him to New York, which will inevitably lead to a run-in with a certain American homicide detective.
1. 1: We've Got Company

Chapter One: We've Got Company

Richard Castle slowly spins his chair in circles, desperate to find something to entertain himself. There is absolutely nothing to do. The case he and Beckett were assigned is finished.

He's happy that they caught the killer, of course, but that means paperwork. And Castle doesn't do paperwork. That is a benefit -and his excuse of getting out of helping out with some of it- of not being a police officer.

He supposes he could go back to his apartment. His publisher has been on his case to crank out a few more chapters of his latest novel, but Castle doesn't think he can concentrate on his own thoughts with the sound of Alexis's new boyfriend running the blender all day long.

* * *

"You could help out a little, you know," Kate Beckett glances up from the pile of papers that has accumulated on her desk.

"Really? A _civilian _tampering with official NYPD records? That has to be breaking some sort of rule," Castle responds.

"I highly doubt anyone would care, and breaking the rules has never stopped you before," Beckett retorts. _Typical Castle. Always front and center when we're chasing criminals, but never available when something can't hold his interest. _"If you're so bored, why don't you go home? You could get some writing done."

"Because it is not possible to get _anything _done at my apartment," Castle whines.

Beckett gives him an exasperated sigh, rolling her eyes. Though she has to admit, Castle isn't the only one who's bored out of their mind.

She focuses on the movements of the pen across the paper, wishing the time wouldn't drag along so mercilessly. Despite her love for the job, Beckett is counting down the hours until she is dismissed and is able to leave.

"Are you sure no one's been murdered?" Castle asks.

"For the third time, Castle, yes," Beckett says, irritated. "But if you don't close your mouth, that's going to change."

"Fine," Castle complains, reluctantly plunging himself into silence.

After what seems like the longest time, Castle's seemingly endless boredom is extinguished, and all it took was a simple phone call.

"This is Detective Kate Beckett," Beckett holds the phone to her ear, relieved to get a break, even if it might be a short one.

"I'm on my way," she hangs up the phone. "C'mon, Castle."

"Murder?" he grins with a little too much excitement in his voice when dealing with death. "I'll get my jacket."

"Not a murder, a B&E," Beckett corrects, holding the elevator for him.

"Not that I'm complaining, but why are they sending a homicide detective to deal with a B&E?" Castle asks, already running through possible explanations in his mind.

"Because the house belonged to the killer from our last case. They seem to think it might be connected," Beckett informs him. It does seem strange; they've already caught the guy.

* * *

"Sherlock, _Sherlock! _Let's get out of here," John Watson lingers just inside the doorway, whereas Sherlock has already begun to explore the house in its entirety.

Just as he suspected, John receives no reply.

"Sherlock, this is a _crime scene. _Not to mention it's in a different country. You don't have jurisdiction here," John calls, though he doesn't have high hopes of getting through to his friend.

* * *

Sherlock Holmes moves swiftly through the home, but slow enough to take in every detail of his surroundings. There is just no way this man could have killed Jeffrey Davis.

He's not sure how anyone could have suspected him after taking one look at his home. He supposes that's what happens when inferior minds are tasked with "complex" puzzles like this.

But this one is too easy. How could they have missed it?

* * *

The wailing of sirens and flashing of lights are quick to grab John's attention. It only takes one glance out the window to confirm his suspicions. The police are here.

"Oh no," John sighs. Why does this kind of thing always happen. Why can't he and Sherlock work one bloody case without running into trouble?

The door flies inward, and a woman with curly brown hair makes her way inside, gun in hand. A man with dark hair follows close behind, though he doesn't appear to be an officer.

John raises his arms in surrender, not wanting to be mistaken for a threat, when Sherlock enters the room.

"I've figured it out," Sherlock announces proudly. Then, he notices the other people who have joined he and John int the living room. "Oh, I see we have company."

"You're both under arrest," Kate Beckett snaps a pair of cuffs on each of the men, but what confuses her is what exactly the tall man with dark, curly hair has "solved".

Sherlock carefully absorbs the information that has been presented to him. The woman has clearly been working as a police officer for a while -a detective, maybe? However, the man accompanying her is not affiliated with the law enforcement; that is blatantly obvious due to his lack of a weapon and the fact that his vest has "WRITER" inscribed on it instead of "POLICE".

"We have a few questions for you," Beckett leads the pair to the car.

**Thanks for reading. I hope you like the first chapter of this story. This is set in season six of _Castle _and before the fall in _Sherlock. _Please leave me a review with your thoughts and comments!**

**Disclaimer: I do not own _Sherlock _or _Castle._**


	2. 2: Always Clever

Chapter Two: Always Clever

"For the record, Mr. Holmes, have you been informed of your rights?" Detective Beckett takes confident strides into the interrogation room, Castle following closely at her heels.

Kate Beckett has always felt at home in the interrogation room. It's where she possesses complete control of her surroundings. The rush of adrenaline courses through her veins with the sense that she is so close to convicting a killer and closing a case.

But this one feels different.

"Yes," Sherlock says. He wishes he could get this over with. This is wasting precious time. The killer could be long gone by now.

"Now, would you like to explain why you and your friend were in Jeffrey Davis's house today?" Beckett takes a seat next to Castle.

"I was solving a case," Sherlock informs the detective. "Tell me, Detective, was it your mother or your father?"

"What?" Beckett seems taken aback by the question.

"Which one of your parents died?" Sherlock continues.

"How did you know-" she begins.

"Simple. The watch on your wrist -it's a man's watch, which would suggest it was your father who passed. But when I was walked in, I passed by your desk. On it, were pictures of you with a man old enough to be your father -they looked current, whereas the photographs of you with a woman, who I assume to be your mother, are much older. Now, you could have had a falling out and have broken contact, but that seems unlikely," Sherlock deduces easily, watching the stunned reaction on the detective's face. "So, I am led to believe you have lost your mother."

Kate Beckett remains silent, not out of sorrow, but out of pure astonishment. Never in her lifetime has she seen anyone who is able to do this.

"Am I wrong?" Sherlock persists.

"No," Beckett answers.

"Do me next," Castle says excitedly, a grin plastered on his face.

"Castle," Beckett scolds.

"Alright, let's see," Sherlock begins, intently studying the man in front of him. "You're clearly not a detective, nor do you have any affiliation with the police other than your shadowing of Detective Beckett. You have gathered enough information to write hundreds of books, yet you stay -probably because of your relationship. Also, you have become accustomed to the excitement of solving crimes."

"That was awesome!" Castle exclaims, a giddy smile plastered on his face.

"Was I right?" Sherlock asks. He needs confirmation that his deductions are correct. He always has.

"Yeah," Castle still hasn't gotten over how cool that was. Maybe the character for his next book could have the abilities of this man.

"Can we get back to why you broke into that house now?" Beckett asks, though it sounds more like an order.

"I suppose we could continue with these frivolous questions, but know that every second wasted in here is another that a murderer walks free," Sherlock answers, absent-mindedly drumming his fingertips on the table.

"What are you talking about?" Beckett says. This is by far the strangest interrogation she's ever experienced.

"I am a consulting detective at Scotland Yard. I am here in pursuit of a serial killer who I believe has killed Jeffery Davis," Sherlock states flatly.

"Really? _You're _a consulting detective at Scotland Yard?" Beckett asks suspiciously.

"Why is that so hard to believe?" Sherlock muses. "If you need confirmation, you may contact my brother. I believe he is in a high enough position to assure you of my authenticity."

"Does your brother work for the government?" Castle asks.

"I suppose you could say that," Sherlock answers.

"That still doesn't explain why you were in my suspect's house," Beckett continues with the interrogation.

Sherlock sighs. "The fact that you could think for one second that this man killed Mr. Davis speaks volumes about the capabilities of those assigned to his case."

"Excuse me?" Beckett says.

* * *

"I told you not to be clever," John sighs when he sees the look of annoyance and exasperation on the detective's face as Sherlock is led back to his cell.

"It's not something I can control, John," Sherlock responds defensively.

"You might want to start learning how to," John says as he is lead to the interrogation room.

"For the record, Mr. Watson, have you been informed of your rights?" Detective Beckett asks. That question is so familiar to her that it is practically second nature.

"Yes," John answers.

"Now, why did you break into Stephen Willam's house today?" Beckett continues, hoping this man will be more compliant that his friend.

"Sherlock insisted that he could discover who killed Jeffrey Davis by going to that man's house. I was simple dragged along. Sherlock can be quite... persistent," John answers.

"How exactly did he think he was going to find the killer?" Beckett asks.

"Absolutely no idea. He does that often, dragging you God knows where for no apparent reason, but if Sherlock says he can find the killer, then I have no doubt that he can," John replies.

"Is he always like that?" Castle asks.

"You have no idea," John responds.

There is a knock on the interrogation room's door, and a man opens it slightly, motioning for the detective. Kate leaves the table and walks over to Detective Ryan, who is waiting for her.

"You're kidding," Beckett says.

**Thanks for reading! I hope you liked this chapter. Sorry to end on a cliffhanger like this. Wait... no I'm not. Please leave me a review and be sure to check out my other stories!**


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